Wireless networks generally include a number of user devices, often referred to as user equipments (UEs), that transmit information wirelessly with network infrastructure equipment, typically referred to as “base stations” or eNode B (“eNB”) equipment. Generally, the interactions between user equipment and infrastructure equipment is defined in accordance with established, standardized air interface standards, such as second generation, third generation, fourth generation air interface standards.
Generally, infrastructure equipment configured with the appropriate hardware and software components to have larger geographic coverage area within a wireless network are typically referred to as macro cells. In a typical configuration, a wireless network service provider defines a planned distribution of macro cells within a geographic area to form the wireless network. A wireless network made primarily of macro cells (e.g., a homogeneous network) can be carefully designed prior to its implementation and can be further optimized based on the known performance characteristics of the macro cells.
In order to improve performance or capacity of a wireless network, a wireless network service provider may implement a number of macro cells, in a manner similar to a homogeneous network, along with additional infrastructure equipment having different performance and operating characteristics than the macro cells, generally referred to as a heterogeneous network. Generally, the additional infrastructure equipment typically implement the same air interfaces as macro cells (e.g., eNBs), but often are much smaller in size and have smaller geographic coverage areas. Such additional infrastructure equipment can be referred to as a small cell, pico cell or femto cell. For example, small cells may be used to provide additional wireless network coverage within buildings, in between geographic boundaries of macro cells, in geographic areas having a large number of user devices (e.g., “hotspots”), and the like. In heterogeneous network implementations, signaling protocols, such as X2, have been implemented to facilitate handover decisions between the different eNBs such macro cell to macro cell handovers, macro cell to small cell handover, and small cell to small cell handovers.
As is generally known, in accordance with certain air interface standards, such as the long term evolution (“LTE”) air interface standard, infrastructure equipment (macro cells and small cells) is configured to transmit information across the entire frequency bandwidth available for transmission. Unlike other air interface standards, such air interface standards, e.g., LTE, do not typically allocate portions of the available frequency bandwidth to eNBs in a wireless network. Rather every eNB in the wireless network attempts to utilize the entire frequency bandwidth to communicate information to user equipment in the geographic region served by the eNB. As such, without any type of adjustment to the configuration of eNBs implementing LTE, an LTE-based wireless network may experience heavy interference at overlapping portions of geographic boundaries of the eNBs. Such an implementation can be referred to as full frequency reuse and can be associated with degrading communications in geographic areas experiencing heavy interference.
In view of the potential for interference among cells in a homogeneous and heterogeneous network implementing air interfaces, such as LTE, various inter-cell interference coordination (ICIC) techniques have been developed to mitigate or minimize interference. One approach to ICIC, referred to as hard frequency reuse, relates to the distribution of portions of the available frequencies among the cells in a heterogeneous network. As applied to the LTE air interface standard, for example, a hard frequency reuse approach would involve subdividing portions of the available frequency bandwidth, generally referred to as sub-carriers, into disjoint sets. The formed disjoint sets of subcarriers would be then assigned to the individual eNBs within a heterogeneous or homogeneous network in a manner that would attempt to avoid adjacent eNBs or cells being assigned to the same set of sub-carriers. While hard frequency reuse approach can significantly mitigate interference between adjacent cells, the spectrum efficiency of the wireless network would like decrease significantly.
Another approach to ICIC corresponds to the combination of aspects of full frequency reuse and hard frequency reuse and is referred to as fractional frequency reuse. In a typical fractional frequency reuse embodiment, the available frequency spectrum is divided into two parts that implement different frequency reuse approaches. A first portion of the frequency spectrum is used in all cells, akin to a full frequency reuse approach. A second portion of the frequency spectrum is divided among different adjacent cells, akin to hard frequency reuse approach. In a practical implementation, a wireless network implementing fractional frequency reuse would assign, or otherwise utilize the full frequency reuse portion of the frequency spectrum to communicate with equipment that are substantially within the coverage area of a single cell. Such devices are often referred to as center cell devices or UEs. Additionally, the wireless network would then assign, or otherwise utilize, the hard frequency reuse portion of the frequency spectrum to equipment within the borders of multiple cells. Such devices are often referred to as cell edge (CE) devices or UEs.
Yet another approach to ICIC, referred to as soft frequency reuse, relates to cells in a heterogeneous or homogeneous network transmitting across of the entire available frequency spectrum. However, in a soft frequency reuse approach, each cell may be configured with varied power transmission levels across sub-carriers. More specifically, adjacent cells may coordinate such that they do not transmit at the same power level for the same sub-carriers. Accordingly, a cell with a higher power configuration for particular sub-carriers would experience less interference from an adjacent cell with a lower power configuration for the same sub-carriers.
Many ICIC techniques, such a hard frequency reuse, fractional frequency reuse and soft frequency reuse, can be implemented in a manner that is static in nature. Such static approaches are not well suited for user equipment traffic loads that may be uneven or subject to change. For example, a heterogeneous network including multiple small cells may experience heavy traffic loads at one or more small cells, but only for a defined period of time (e.g., a small cell having a geographic area corresponding to a cafeteria). Current approaches to dynamic analysis of interference scenarios among cells are generally not efficient to analyze potential interference scenarios across an entire frequency spectrum.